LEDs are solid-state light-emitting devices formed from semiconductor materials that comprise, in generally, III-V compound elements such as gallium phosphide, gallium arsenide, or gallium nitride. By biasing the compound semiconductor, massive electrons and holes encounter and recombine in an active layer of LED, and electrons will fall to lower energy levels with the emission of photons. Therefore, the electrical energy is converted to the light to achieve the effect of light emission.
In the traditional LED structure, electrodes might absorb the light emitted from the active layer, such that the expected light-emitting performance of LED is reduced. Moreover, the light absorbed by the electrodes will be converted into heat, resulting in gradual increase temperature in the electrodes or overheating condition. Thereby, improvement is required.
In order to reduce the absorption of light emitted from the active layer, one of prior arts is to form a reflection layer under electrodes of an LED. Thereby, the absorption is avoided when the light emitted from the active layer contact the electrodes. In addition, because the side surface of the active layer may emit the light, the reflective layer may have a special shape such as ladder- or L-shaped in a cross-section view, so that the light can be multi reflected via the reflection layer and thus enhancing the light-emitting efficiency of LED.
However, the prior art, which is required to add reflection layers under electrodes of LED, increases complexity in fabrication process of LED. Besides, according to different light-receiving conditions under the positive and negative electrode of LED, the reflection layers shall have different structures respectively, that also increase complexity in the fabrication process.